src/HOL/Tools/Sledgehammer/clausifier.ML

--- a/src/HOL/Tools/Sledgehammer/clausifier.ML	Tue Jun 29 10:36:36 2010 +0200
+++ b/src/HOL/Tools/Sledgehammer/clausifier.ML	Tue Jun 29 10:56:45 2010 +0200
@@ -7,9 +7,9 @@
 
 signature CLAUSIFIER =
 sig
-  val cnf_axiom: theory -> thm -> thm list
+  val cnf_axiom: theory -> bool -> thm -> thm list
   val cnf_rules_pairs :
-    theory -> (string * thm) list -> ((string * int) * thm) list
+    theory -> bool -> (string * thm) list -> ((string * int) * thm) list
   val neg_clausify: thm -> thm list
   val neg_conjecture_clauses:
     Proof.context -> thm -> int -> thm list list * (string * typ) list
@@ -193,7 +193,7 @@
 (* Given the definition of a Skolem function, return a theorem to replace
    an existential formula by a use of that function.
    Example: "EX x. x : A & x ~: B ==> sko A B : A & sko A B ~: B"  [.] *)
-fun skolem_theorem_of_def thy rhs0 =
+fun skolem_theorem_of_def thy cheat rhs0 =
   let
     val rhs = rhs0 |> Type.legacy_freeze_thaw |> #1 |> Thm.cterm_of thy
     val rhs' = rhs |> Thm.dest_comb |> snd
@@ -213,10 +213,13 @@
       THEN rtac ((prem |> rewrite_rule skolem_id_def_raw)
                  RS @{thm someI_ex}) 1
   in
-    Goal.prove_internal [ex_tm] conc tacf
-    |> forall_intr_list frees
-    |> Thm.forall_elim_vars 0  (*Introduce Vars, but don't discharge defs.*)
-    |> Thm.varifyT_global
+    (if cheat then
+      Skip_Proof.make_thm thy (Logic.mk_implies (pairself term_of (ex_tm, conc)))
+    else
+      Goal.prove_internal [ex_tm] conc tacf
+      |> forall_intr_list frees
+      |> Thm.forall_elim_vars 0  (*Introduce Vars, but don't discharge defs.*)
+      |> Thm.varifyT_global)
   end
 
 (*Converts an Isabelle theorem (intro, elim or simp format, even higher-order) into NNF.*)
@@ -229,11 +232,12 @@
   in  (th3, ctxt)  end;
 
 (*Skolemize a named theorem, with Skolem functions as additional premises.*)
-fun skolemize_theorem thy th =
+fun skolemize_theorem thy cheat th =
   let
     val ctxt0 = Variable.global_thm_context th
     val (nnfth, ctxt) = to_nnf th ctxt0
-    val sko_ths = map (skolem_theorem_of_def thy) (assume_skolem_funs nnfth)
+    val sko_ths = map (skolem_theorem_of_def thy cheat)
+                      (assume_skolem_funs nnfth)
     val (cnfs, ctxt) = Meson.make_cnf sko_ths nnfth ctxt
   in
     cnfs |> map introduce_combinators
@@ -245,13 +249,13 @@
 
 (* Convert Isabelle theorems into axiom clauses. *)
 (* FIXME: is transfer necessary? *)
-fun cnf_axiom thy = skolemize_theorem thy o Thm.transfer thy
+fun cnf_axiom thy cheat = skolemize_theorem thy cheat o Thm.transfer thy
 
 
 (**** Translate a set of theorems into CNF ****)
 
 (*The combination of rev and tail recursion preserves the original order*)
-fun cnf_rules_pairs thy =
+fun cnf_rules_pairs thy cheat =
   let
     fun do_one _ [] = []
       | do_one ((name, k), th) (cls :: clss) =
@@ -259,7 +263,7 @@
     fun do_all pairs [] = pairs
       | do_all pairs ((name, th) :: ths) =
         let
-          val new_pairs = do_one ((name, 0), th) (cnf_axiom thy th)
+          val new_pairs = do_one ((name, 0), th) (cnf_axiom thy cheat th)
                           handle THM _ => []
         in do_all (new_pairs @ pairs) ths end
   in do_all [] o rev end